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Static Electric Discharge Hazard on Bulk Oil Tank Vessels

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Static Electric Discharge Hazard on Bulk Oil Tank Vessels Static Electric Discharge Hazard On Bulk Oil Tank Vessels Phase 1 Report Prepared for: Commandant G-MTH-2, Engineering Branch US Coast Guard Headquarters 2100 2nd Street, SW Washington, DC 20593-0001 Prepared by: Michael G. Dyer, DTS-73 The Volpe National Transportation Systems Center 55 Broadway, Kendall Square Cambridge, Massachusetts 02142-1093 For more information on this report contact: Guy Collona and Bob Benedetti National Fire Protection Association Batterymarch Park Quincy, Massachusetts 02269 Michael Dyer US Department of Transportation Research and Special Programs Administration John A. Volpe National Transportation Systems Center Kendall Square Cambridge, Massachusetts 02142 1 Table of Contents 1. Executive Summary 2. Introduction and Background .1 The problem .2 Accident history .3 Safety measures in place .4 Project goals 3. Recent Accident History .1 FIONA .2 AMERICAN EAGLE .3 Tank barge TT 103 .4 Tank barge STC 410 .5 Tank barge Hollywood 1034 .6 Other accidents .7 Overview 4. The Electrostatic Hazard .1 Four conditions required for explosive ignition .2 Mechanisms for producing hazardous conditions .1 Static generation .2 Accumulation of charge and potential .3 Spark discharge .4 Flammable vapor 5. Corrective and Preventative Measures .1 Mitigation of static generation .1 Loading precautions .2 Displacing of lines .3 Precaution against mist and steam .4 Precaution for crude oil washing (COW .5 Precaution for overall loading .6 Air injection precaution .7 Precaution for combination carriers .2 Prevention of charge accumulation .1 Antistatic additives .2 Relaxation of static accumulators .3 Non-accumulating piping, wands, etc. .4 Tank washing .5 Filters .6 Mopping .7 Carbon dioxide .3 Prevention of spark discharge .1 Bonding and grounding .2 Dipping and ullaging .3 Tank cleaning .4 Loose objects .5 Free fall of liquids .6 Gas freeing 2 .7 Inert gas precaution .8 Carbon dioxide .4 Control of vapor composition .1 Definition of tank atmospheres .2 Water washing .3 Gas freeing .4 Steam cleaning of tanks .5 Switch loading .6 Securing of covers .5 Exceptions .6 General 6. Conclusions and Recommendations .1 Conclusions .2 Recommendations Bibliography 3 Section 1. Executive Summary This report examines the problem of electrostatic ignition as the cause of explosions on tank vessels, recounts recent accident history, and surveys the safety guidance now available to industry. It is the deliverable product of Phase 1 of a two phase project to improve industry's safety record in this area. The report finds that extensive safety information is available in a number of publications, which offer, , for the. most part, consistent guidelines to deal with the static electricity hazard. Much of the guidance is general in nature, and many companies do not f ill information gaps with internally developed procedures and training. The problem has persisted as violations of many fundamental safety procedures have caused serious accidents. A Coast Guard safety guide, issued as an enclosure to a Navigation and Vessel Inspection Circular (NVIC), could improve tank vessel safety if properly targeted at industry sectors, perhaps as separate volumes. A conference of industry, government, and standards experts would be a good first step in the development of such documentation. The Volpe Center recommends that the Coast Guard proceed with Phase 2, the development of the safety field guide. Section 2. Introduction and Background The Engineering Branch of the Coast Guard Office of Marine Safety, Security, and Environmental Protection (G-MTH-2) has, as a result of several recent accidents involving substantial losses of life and property, recognized the persistent danger of tank vessel explosions caused by electrostatic discharge. The Volpe National Transportation Systems Center was tasked to study the incidence of these explosions and the pertinent safety measures currently in place. The physical phenomena of the static discharge hazard were not investigated for this report. This report presents the results of the study with a compilation of safety standards, procedures, etc. promulgated by government and industry. The project plan calls for a second phase, in which a static electricity field guide will be developed for use by industry. 2.1 The Problem Electrostatic discharge has long been known as a hazard associated with the handling of petroleum products. A monograph by Klinkenberg and van der Minne in 1958 [1] led to the development of anti- static additives by Royal Dutch/Shell. J.T. Leonard [2] has described many papers and publications from the 1960s and 1970s addressing both the hazard and related safety measures; they deal primarily with static generation during fuel loading. The National Fire Protection Association (NFPA) states, in NFPA 77 "Static Electricity", that "Static electrification and the various effects that result from the positive and negative charges so formed may constitute a fire or explosive hazard. The generation of static electricity cannot be prevented absolutely, because its intrinsic origins are present at every interface" [3]. 4 Static electricity is generated when liquids move in contact with other materials. This is a common occurrence when liquid is being moved through pipes, mixed, poured, pumped, filtered, or otherwise agitated. Other causative processes include the settling of solids or immiscible liquid through a liquid, the ejection of particles or droplets through a nozzle, and the splashing of a liquid against a solid surface. NFPA 77 states that "under certain conditions, particularly with liquid hydrocarbons, static may accumulate in the liquid", with the danger of subsequent sparking in a flammable vapor-air mixture. The problem is broad-based, including the marine shipping industry (about 2000 tankers and upward of 4000 tank barges) and shore-based industries involved in vessel maintenance and repair. The latter includes 10,000 vacuum trucks in the United States which are commonly used for oil removal and hazardous waste transport. [4] The solution for government and industry is to communicate the various means of counteracting these phenomena to all concerned, including fleet and terminal operators, tankermen, and shipyards and other tank cleaning concerns. 2.2 Accident History A number of serious accidents occurred when very large crude carriers (VLCC) first came into service in 1969 (MACTRA, MARPESSA, KONG HAAKON IV). Water washing techniques then in use caused the generation of large static charges in the cargo tanks, whose unprecedented size was a causal factor. Oil shippers took steps to control the atmosphere in the tanks by either 1) careful stripping and gas freeing or 2) assuring an over-rich mixture in the tanks. The problem in this particular sector has been largely eliminated by .the use of crude oil washing (COW) techniques or of smaller water washing machines. More recently, several tanker and tank barge explosions in which static discharge was a probable cause have refocused attention on the mechanisms of electrostatic discharge and the applicable safety standards. The SURF CITY, FIONA, AMERICAN EAGLE, CIBRO SAVANNAH (barge), tank barge TT 103, tank barge STC 410, and the tank barge Hollywood 1034 accidents each offered safety lessons to be (re)learned. In most cases, routine cargo tank operations such as loading, stripping, or cleaning were underway. Correspondence with industry representatives has revealed a history of accidents caused by electrostatic discharge in tank trucks (particularly at loading racks) and storage tanks. One expert said that chemical storage tanks in particular have many static related explosions. Publicly available information on these incidents is, however, scant. 2.3 Safety Measures in Place There is ample documentation in place describing safety precautions to be taken against static discharge. The most important industry publications are the following: · International Safety Guide for Tankers and Terminals ISGOTT [5]: This is the industry standard and most often the basis for safety documents internally produced by the oil shippers. A copy of ISGOTT may be found on board most ships and in most terminals. It has the most thorough treatment of electrostatic hazards on tank vessels. ISGOTT is produced by a consortium of the Oil Companies Marine International Forum, the International Chamber of Shipping, and the International Association of Ports and Harbors. 5 · American Petroleum Institute Recommended Practice 2003 (API 2003) "Protection Against Ignitions Arising out of Static, Lightning, and Stray Currents" [6]: This document presents current technology in the prevention of hydrocarbon ignition by static electricity, lightning, and stray currents. It contains good general principles of safety, but concentrates largely on land based oil storage and transportation. API 2003 refers often to ISGOTT on matters of marine transportation. · NFPA 77 "Recommended Practice on Static Electricity " [2]: This document is a more general treatment of static hazard in all industries. It is short on the subject of tankers and barges, but a good source for general principles. NFPA 77 is prepared by the NFPA Technical Committee on Static Electricity, made up of experts from industry and government. · American Waterways Shipyard Conference "Safety Guidelines for Tank Vessel Cleaning Facilities" [7]: This document was prepared expressly for shore based facilities involved in the cleaning of tank vessels, and uses relevant portions of ISGOTT and input from the affected
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